Refrigerating apparatus



Feb. 16, 1937; G. c. PEARCE REFRIGERATING APPARATUS Filed NOV. 30, 1932 Sheets-Sheet l Feb. 16, 1937. c, PEARCE 2,070,748

REFRIGERATING APPARATUS Filed Nov. 50, 1932 2 Sheets-Sheet 2 Patented Feb. 16, 192.7

UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS George C. Pearce, Dayton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation of Delaware Application November 30, 1932, Serial No. 645,021

6 Claims. (Cl. 62-4) This invention relates to refrigerating appara- :us and more particularly to refrigerating systems which are provided with means for automatically defrosting the evaporating means at timed periods.

It is customary in refrigeration to maintain the evaporating means at freezing temperatures. This causes the accumulation. of frost upon the evaporating means which acts as insulation and thereby reduces the efficiency and the capacity of the refrigerating system. It is therefore desirable that this accumulation of frost be kept at a minimum and for this reason instructions are ordinarily given with each refrigerating system to pull the electric plug or in some other way to break the circuit of the electric motor which drives the compressor frequently in order to allow the evaporating means to warm up and to allow the frost to melt therefrom.

These instructions are not always faithfully followed and it is therefore one of the objects of my invention to provide chronometric means which will open the electric circuit of the compressor driving motor at -timed periods to permit the frost to periodically melt from the evaporating means.

When the evaporating means is defrosted automatically at timed periods, it sometimes happens that the defrosting period occurs at an inopportune time, for example, when it is desired to freeze ice cubes or desserts within the evaporating means. It is therefore another object of my invention to provide a manual means, which may at any time be operated by the housewife to prevent the occurrence of one or more of the timed defrosting periods provided by a chronometric defrosting means.

When it is desired to freeze ice cubes or desserts, the temperature regulator, which is widely used on domestic refrigerators, is changed to a colder position. In order to reduce the number of things required of the housewife to properly control her refrigerator, it is another obinvention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In'the drawings:

Fig. 1 is a diagrammatic representation of a refrigerating system incorporating my improved automatic defrosting means;

Fig. 2 is a view in elevation of a practical embodiment of the defrosting means shown in Fig. 1, and

Fig. 3 is a sectional view taken along the lin 3-3 of Fig. 2.

Referring to the drawings and more particularly to Fig. 1, there is shown a compressor 20 for compressing the refrigerant and for forwarding the refrigerant to the condenser 2| where the compressed refrigerant is liquefied and collected in a receiver 22. From the receiver 22 the liquid refrigerant is forwarded through a supply conduit 23 to a suitable valve 24 such as an automatic expansion valve which controls the flow of liquid refrigerant to an evaporating means 25. The liquid refrigerant within the evaporating means 25 absorbs heat and vaporizes, this vapor being returned to the compressor through the return conduit 26.. The compressor 20 is driven by an electric motor 21 through suitable pulley and belt means 28. The electric motor 21 is supplied with electric energy through an electric circuit generally designated by the reference character 29.

In order to control the operation of the electric motor, I have provided an automatic switch means which incorporates an automatic defrosting means. In the diagrammatic illustration there is provided a bellows 30 which is connected by a tube 3| to a thermostatic bulb 32 mounted in heat exchange relation with the evaporating] means 25. The thermostatic bulb 32 contains a volatile liquid which generates pressure according to the temperature of the evaporating means. This pressure is transmitted to the bellows 30 which acts upon the lever 33 to open and close the switch contacts 34 which open and close the electric motor circuit 29 to stop and start, the motor 21.

I also provide a temperature regulator for such a switch for the purpose of regulating a temperature of the evaporating means 25. This temperature regulator has a spring 35-which acts upon the lever 33 and opposes the expansion of the bellows 30. The tension upon this spring is adjusted by a temperature regulating screw 36. By varying the tension on the spring 35,- the temperature and pressure at which the switch contacts 34 open and close is adjusted.

The evaporating means is normally maintainedinsulator for the evaporating means and prevents effective heat transfer which reduces the efllciency and capacity of the evaporating means and also the entire refrigerating system. I propose to permit the evaporating means to warm up periodically and automatically so that the frost will melt from the evaporating means at frequent intervals so that the accumulation of frost on the evaporating means is kept at a minimum. In order to do this, I provide a synchronous electric clock motor 40 which drives through suitable reduction gears a cam 4|. This cam acts upon a switch contact member 42 to open a set of switch contacts 43 at time intervals so as to cause the electric motor 21 to be stopped for a sufficient period of time to cause the evaporating means to warm, up sufficiently to melt the accumulated frost therefrom each time the cam 4| completes a revolution.

With such a chronometric defrosting means, it is likely that at sometime this defrosting period will occur at an inopportune time. For this reason I have provided a shunt 44 around the switch contacts 43 and provided this shunt 44 with a separate switch 45 so that, should the defrosting period occur at an inopportune time, the switch 45 may be closed so as to prevent the chronometric defrosting means from effectively opening the electric motor circuit 2 I. This switch 45 may be opened and closed by separate manually controlled means but I prefer to cause it to be opened and closed in conjunction with the movement of the manual temperature regulator 36. As shown, the temperature regulator 36 is in the extreme cold position. The temperature regulator 36 moves a nut 41 upwardly and downwardly to vary the tension of the spring 35. This nut 41 has a contact 48 mounted thereon, which contacts with a stationary contact 49 when the nut 41 is in its upperor colder positions. However, when the temperature regulator is turned to normal position in which the nut 41 is in its lowermost position, the contact 48 is in a position beneath the stationary contact 49 so that the shunt circuit 44 is open atall times when the temperature regulator is in normal position. Hence, whenever the temperature regulator is in normal position, the chronometric defrosting means is operative. However, when the temperature regulator is in a position colder than normal, the switch 45 is closed and the chronometric defrosting means becomesinoperative to prevent the operation of the compressor driving motor 21.

In Figs. 2 and 3 there is shown a practical embodiment of the switch and automatic defrosting means. In this embodiment there is provided a bellows 60 corresponding to the bellows 30 of Fig. 1, which acts upon a switch follower lever 8| which is pivoted at one end upon a sort of a knife edge 62. The lever 6| is connected at its movable end to a double-toggle switch mechanism comprising a secondlever 63, and a toggle spring 64 which connects the second lever to an ear 66 upon the irregularly shaped switch contact lever 65 enclosed within a housing 59. A

' pair of movable contacts 61 are provided at the lower end of the switch contact lever 65. These contacts are adapted, when closed, to bridge a pair of stationary contacts 88 to close the electric motor circuit.

In order to control the pressure and temperature at which the'switch contacts open and close,-

" I have provided a temperature regulating spring 69 which at its upper end rests against a nut II threaded upon a temperature regulating screw H and which rests against a spring retainer I2 at its lower end which rests in turn upon the upper surface of the lever 8|. The temperature regulating screw II is provided with a knob I3 upon its upper end by which the housewife can regulate the temperature of the evaporating means. a

In order to provide for periodic defrosting I provide a set of stationary contacts 15 in series with the stationary contacts 68 which are normally bridged by a set of movable contacts 1O mounted upon the lower end of the defrosting switch lever ll which is pivoted at I8. A synchronous electric clock motor 19 is connected in parallel with the compressor motor circuit and drives through a pinion'lll, a large gear 8|, a second pinion 82, and a large gear 83 to rotate a cam 84 provided with a nose 85 which engages the upper end 86 of the defrosting switch contact lever 11 to ,open the contacts and 16 to provide a defrosting period.

In order to prevent the occurrence of a de-- frosting period whenit is desired to freeze desserts or ice cubes, I provide a shunt 88 around the defrosting set of contacts and provide a switch a 89 in the shunt having a movable contact 80 mounted upon the temperature regulating nut 10 which is adapted to engage a spring mounted stationary contact 9| while the temperature regulating knob is in any one of the colder than normal positions. In this way whenever it is desired to prevent the occurrence of a defrosting cycle, it is merely necessary to turn thetemperature regulator to any one of the colder positions. Inasmuch as it is ordinarily desired to prevent the occurrence of a defrosting period during the freezing of any desserts or ice cubes, and since in such instance the housewife will turn the temperature regulator to one of the colder positions, it is not necessary for the housewife to bother herself about the automatic defrostving means since this is rendered inoperative whenever the temperature regulator is moved to one of the cold positions. When the temperature regulator is returned to normal position, the movable contact 90 is lowered sufficiently to. disengage itself from the lower curled end of the springmounted stationary contact ill and in this way the switch 89 is opened and the chronometric defrosting means is again rendered operative. The chronometric defrosting means thus operates without attention on the part of the housewife.

By chronometric means, I meanany-sort of time measuring device such as an ordinary elecapparatus for periodically raising the temperature-of the evaporating means above water freezing temperatures, manual means operable at will for effecting the control of the apparatus for temporarily lowering below normal the temperature of the evaporating means, and means rendered effective by said manual means for render ing the chronometric means ineffective for varying the temperature of the evaporating means.

2. Refrigerating apparatus including an evaporating means, means for circulating liquid refrigerant through the evaporating means, control means for normally maintaining the temperature of the evaporating means between predetermined limits, means for temporarily modifying the operation of the circulating means to obtain temporarily a lower temperature in said evaporating means, chronometric means for automatically modifying the operation of the circulating means to obtain temporarily a higher temperature in said evaporating means, and means cooperating with said temperature modifying means and with said chronometric means for rendering the chronometric means ineffective whenever the temperature modifying means becomes operative.

3. Refrigerating apparatus comprising a refrigerant liquefying means including a compres= sor, an electric motor circuit and an electric motor for driving the compressor, a refrigerant evaporating means operatively connected'to the refrigerant liquefying means, control means for opening and closing the electric circuit to nor-' means for preventing the opening of the electric circuit by the chronometric means.

4. A refrigerator control including pressure responsive means for opening and closing an electric circuit at predetermined low and high pressures, means operable at will for temporarily modifying the operation of the pressure responsive means to cause the opening and closing of the electric circuit at other pressures, chronometric means for periodically opening the electric circuit, and means rendered effective by the means operable at will for rendering the chronometric means ineffective for opening the electric circuit.

5. A refrigerator control including pressure responsive means for opening and closing an electric circuit at predetermined low and high pressures. means operable at will for temporarily modifying the operation of the pressure responsive means to cause the opening and closing of the electric circuit at other pressures, chronometric means for periodically disturbing the normal control of the electric circuit, and means cooperating with the means operable at will and with the chronometric means for rendering the chronometric means ineffective to disturb the normal control of the electric circuit whenever the means operable at will becomes operative.

6. A refrigerator control including pressure responsive means for opening and closing-an electric circuit at predetermined low and high pressures, means operable at will for temporarily modifying the operation of the pressure responsive means to cause the opening and closing of the eletcric circuit at other pressures, chronometric means for periodically disturbing the normal control of the electric circuit, and means rendered effective by the means operable at will for rendering the chronometric means ineffective for disturbing the normal control of the electric circuit. 7

GEORGE C. PEARCE. 

